The invention relates generally to soldering alloys, and more specifically to soldering alloy compositions useful in hand-soldering of art work or other artifacts where there is a continuing need for soldering compositions which give a bright, smooth finish. High-speed hand-soldering also requires a composition which solidifies rapidly.
A solder can be broadly defined as a fusible metal alloy composition used to bond or coat metals. Solders having distinctly different properties can be obtained by using different combinations of metals, and by varying the relative proportions of each metal. One of the most widely employed solders is a binary composition comprising tin and lead. The relative amounts of tin and lead in tin-lead solder compositions can be varied over relatively wide limits. However, a commonly employed tin-lead solder composition generally comprises about 60% by weight tin with the remainder being lead. Solders containing 50% tin are also well known.
Binary solder compositions are satisfactory for many applications such as bonding together sheet metal parts, and bonding electronic components to circuit boards. Solder compositions can be in the form of a wire, rod or stick and can be melted by a soldering iron, torch, heating wires or the like.
U.S. patent Reissue No. 29,563 (Manko) discloses solder compositions which are useful in automated soldering processes, which solders, in one embodiment, consist essentially of approximately 55% by weight tin, 2.77% by weight antimony, with the remainder being substantially lead. In another embodiment, the preferred composition consists essentially of approximately 52% by weight tin, 3% by weight antimony, with the remainder being substantially lead. The solder compositions are used in liquid form and are retained in a molten state in a reservoir for use in an automated soldering operation. The above-cited patent does not suggest using the disclosed solder compositions in hand soldering operations. Also, in all embodiments, the disclosed compositions contain relatively high amounts of antimony i.e., greater than 1.5% by weight.
U.S. Pat. No. 3,607,252 (North) discloses soldering compositions consisting essentially of 58% to 60% by weight tin, 34.3% to 37.7% lead, 3.8% to 4.2% antimony, and 0.5% to 1.5% copper. The solders disclosed in that patent contain relatively high amounts of antimony and copper and are intended for use in the assembly of products which require both electrical and mechanical connections.
U.S. Pat. No. 4,588,657 (Kujas) discloses solder compositions consisting essentially of about 55% by weight to 65% by weight tin, about 2% by weight to 3.9% by weight calcium and the balance being substantially lead. No antimony is present in the solders.
An ideal composition for many soldering purposes is the tin-lead eutectic, i.e. an alloy which is nominally 63% by weight tin and 37% by weight lead. The eutectic has a sharp melting point at 182.8.degree. C. Use of such a eutectic composition results in fine-grained joints having excellent mechanical properties. However, for many applications, a 63% tin-37% lead solder alloy is less than ideal.
For example, it would be desireable to have a low cost solder alloy composition for articles of manufacture of a decorative or artistic nature utilizing solder alloys to produce a seam, joint or line having a bright, smooth finish and high rounded bead or crown. Such a low cost solder alloy composition should have all the desirable properties of the tin-lead eutectic composition, but with reduced tin content because of the very high cost of tin. It would also be desirable to have a solder alloy that would exhibit excellent handling characteristics so as to facilitate high speed hand soldering operations, and yet result in a bright, smooth joint having good tensile strength.